There is known a substrate processing system equipped with a single-sheet type substrate processing apparatus. As one of this kind of system, there is a substrate processing apparatus having a function of removing a film on a peripheral portion of a substrate by supplying a processing liquid onto the peripheral portion of the substrate from a nozzle while holding the substrate having a film formed on a surface thereof and rotating the substrate around a vertical axis. In Patent Document 1, an imaging unit is provided in the substrate processing system, and an image of the peripheral portion of the substrate processed by the substrate processing apparatus is obtained. Based on the image, it is determined whether the film on the peripheral portion of the substrate is appropriately removed.
Patent Document 1: Japanese Patent Laid-open Publication No. 2013-168429
In case that the imaging unit is disposed at a position facing the peripheral portion of the substrate in the state that the substrate is held by the substrate processing apparatus, a liquid may adhere to or be coated on the imaging unit while processing the substrate with the processing liquid, so that the successful image cannot be obtained. The Patent Document 1 does not mention any solution to such a problem.